1. Field of the Invention
The present invention relates to a light emitting diode substrate assembly, and more particularly to a light emitting diode substrate assembly having multiple light emitting diodes chips mounted directly on a metal substrate.
2. Description of Related Art
A light emitting diode (LED) has capabilities of long useful life, low power-consuming, high brightness, small volume, quick reaction time and so on, the LED is popular and takes the place of the incandescent lamp and fluorescent to serve as a new generation of light source.
With reference to FIG. 12, a conventional LED (71) is mounted on one side of a printed circuit board (PCB) or a metal core printed circuit board (MCPCB) (72), and a heat-dissipating element (73) is mounted on the other side of the PCB (72). Alternatively the conventional LED (71) may be mounted on an aluminum substrate having a dielectric layer and a conductive layer. Accordingly, heat generating during the operation of the LED (71) can be dissipated by the heat-dissipating element (73) or the aluminum substrate through the PCB (72) or the dielectric layer.
However, the PCB or the MCPCB (72) is made of polymer materials and the dielectric layer is made of polymer or ceramic materials, so the heat-conducting capability of the PCB (72)/dielectric layer is low. Therefore, heat generating during the operation of the LED (71) is stored up in the PCB (72) or the dielectric layer, and the heat-dissipating effect to the LED (71) is not sufficient.
Additionally, when the PCB (72) has a thin substrate, the PCB (72) cannot be applied to a high voltage condition. Contrarily, when the PCB (72) has a thick substrate, the heat-conducting capability of the PCB (72) becomes reduced. Therefore, the conventional LED substrate assembly as shown in FIG. 12 cannot be applied for an alternating current (AC) LED.
With reference to FIG. 13A, in a chip on board (COB) technique, a substrate has a recess (81) and multiple direct current (DC) LED chips (82) are mounted in the recess (81) in an array. When packaging, the chips (82) are connected electrically with each other by bonding wires (83). However, when the number of the chips (82) is increasing, the chips (82) are difficulty positioned on precisely desired positions and easily misalign from each other. With the tiny size of electrodes on the chips (82), the wire-bonding process is easily misaligned. To solve the problem, an Optical Alignment System is applied during wire bonding. However, the effect does not meet expectation. Additionally, there is not a reflecting surface formed between the chips (82), lateral light emitting from the chips (82) cannot be efficiently reflected as a light source.
FIGS. 13B and C show LED chip arrays applied for AC LED. However, the LED chip array at most comprises two chips (84) due to the household voltage up to 220V, so the AC LED cannot have more than three chips as shown in FIG. 13A.
To overcome the shortcomings, the present invention tends to provide a light emitting diode substrate assembly to mitigate or obviate the aforementioned problems.